orm: add delete stmt (#5725)

vlib/orm/orm_test.v

@@ -209,6 +209,15 @@ fn test_orm_sqlite() {
 		select from User order by age desc limit 1 offset offs
 	}
 	assert second_oldest.age == 31
+
+	sql db {
+		delete from User where age == 34
+	}
+
+	updated_oldest := sql db {
+		select from User order by age desc limit 1
+	}
+	assert updated_oldest.age == 31
 }
 
 fn test_orm_pg() {

vlib/v/gen/sql.v

@@ -28,8 +28,10 @@ fn (mut g Gen) sql_stmt(node ast.SqlStmt) {
 	g.write('sqlite3_stmt* $g.sql_stmt_name = ${dbtype}__DB_init_stmt($db_name, tos_lit("')
 	if node.kind == .insert {
 		g.write('INSERT INTO `${util.strip_mod_name(node.table_name)}` (')
-	} else {
+	} else if node.kind == .update {
 		g.write('UPDATE `${util.strip_mod_name(node.table_name)}` SET ')
+	} else if node.kind == .delete {
+		g.write('DELETE FROM `${util.strip_mod_name(node.table_name)}` ')
 	}
 	if node.kind == .insert {
 		for i, field in node.fields {
@@ -61,8 +63,10 @@ fn (mut g Gen) sql_stmt(node ast.SqlStmt) {
 			}
 		}
 		g.write(' WHERE ')
+	} else if node.kind == .delete {
+		g.write(' WHERE ')
 	}
-	if node.kind == .update {
+	if node.kind == .update || node.kind == .delete {
 		g.expr_to_sql(node.where_expr)
 	}
 	g.writeln('"));')

vlib/v/parser/sql.v

@@ -127,6 +127,7 @@ fn (mut p Parser) sql_stmt() ast.SqlStmt {
 	}
 	mut inserted_var_name := ''
 	mut table_name := ''
+	if kind != .delete {
 		expr := p.expr(0)
 		match expr {
 			ast.Ident {
@@ -140,6 +141,7 @@ fn (mut p Parser) sql_stmt() ast.SqlStmt {
 				p.error('can only insert variables')
 			}
 		}
+	}
 	n = p.check_name() // into
 	mut updated_columns := []string{}
 	mut update_exprs := []ast.Expr{cap: 5}
@@ -160,7 +162,10 @@ fn (mut p Parser) sql_stmt() ast.SqlStmt {
 				break
 			}
 		}
+	} else if kind == .delete && n != 'from' {
+		p.error('expecting `from`')
 	}
+
 	mut table_type := table.Type(0)
 	mut where_expr := ast.Expr{}
 	if kind == .insert {
@@ -177,6 +182,12 @@ fn (mut p Parser) sql_stmt() ast.SqlStmt {
 		}
 		p.check_sql_keyword('where')
 		where_expr = p.expr(0)
+	} else if kind == .delete {
+		table_type = p.parse_type()
+		sym := p.table.get_type_symbol(table_type)
+		table_name = sym.name
+		p.check_sql_keyword('where')
+		where_expr = p.expr(0)
 	}
 	p.check(.rcbr)
 	return ast.SqlStmt{